One other way to do it is with a power line extender, if you don’t want to run an Ethernet cable. This uses your existing power lines to extend the signal from one room to another, essentially turning your in-wall power wiring into Ethernet. These typically come with two small boxes. One is plugged into your router and a wall power socket. The other is plugged into the room where you need coverage. Many of these broadcast WiFi in that second room, but many alternatively simply provide an Ethernet jack in the second room (which you then plug an access point or WiFi router into, same as if it was Ethernet). The best of these support about half the speed of a cat5 cable, which is usually good enough for most uses.